Computer memory comes in two basic forms: Random Access Memory (hereinafter RAM) and Read-Only Memory (hereinafter ROM). RAM is generally used by a processor for reading and writing data. ROM is generally used for storing data which will never change, such as the Board Input/Output System (hereinafter BIOS).
Generally, RAM makes up the bulk of the computer system's memory, excluding the computer system's hard-drive, if one exists. RAM typically comes in the form of dynamic RAM (hereinafter DRAM) which requires frequent recharging or refreshing to preserve its contents. Organizationally, RAM data is typically arranged in bytes of 8 data bits. An optional 9th bit, a parity bit, acts as a check on the correctness of the values of the other eight bits.
A SIMM (Single Inline Memory Module) is a printed circuit board having, among other things, memory chips and connection points or pins. SIMMs are inserted into special sockets on the computer system's motherboard or memory carrier card. A central characteristic of SIMMs is that although there are connection pins on both sides of the SIMM's printed circuit board, these connections are not singular. That is, pin 1 on the front side of the printed circuit board is connected to pin 1 on the backside of the printed circuit board. Therefore, although most SIMMs have a total of 144 pins, only 72 are available for electrical connection.
A DIMM (Dual Inline Memory Module) is also a printed circuit board having, among other things, memory chips and connection points or pins. DIMMs are also inserted into special sockets on the computer system's motherboard or memory carrier card. However, the DIMM includes a dual row of contacts, one on each side of the printed circuit board, which are available for electrical contact. Most general DIMMs include a total of 168 pins, with 84 pins on the front side and 84 pins on the back side of the printed circuit board. Each pin is available for electrical contact.
SIMMs and DIMMs are available in a variety of organizations (e.g., capacity), voltages, speeds, memory types/cycles, physical dimensions, and buffering. Almost all SIMMs and DIMMs have printed circuit boards which are "keyed" and/or "notched" to prevent them from being inserted backwards or into computer systems with different operating voltages from the SIMM or DIMM being inserted. Given the considerable differences between SIMMs and DIMMs, it is apparent these memory modules are not so easily interchanged. While the fundamental architecture of SIMMs and DIMMs is similar, the self-contained descriptive information (e.g., presence detects or PDs) and the physical form factors (e.g., notches, pins, etc.) are dissimilar. As a consequence of these dissimilarities, computer systems which employ DIMMs cannot readily accept SIMMs. Accordingly, it desired to provide a device which overcomes these considerable differences and allows for the use of SIMMs in computer systems that require DIMMs.